Bowden wire casing



Nov. 16, 1943. A. NELSON BOWDEN WIRE CASING Filed May 17, 1941 FIG. I

FIG.2

INVENTOR ARTHL JR NELSON )D'E. BY

ATTORNEY Patented Nov. 16, 1943 BOWDEN WIRE. C5 39 Arthur Nelson, Brooklyn, Y., assignorto Remington Rand Inc.,-

c De awa Buffalo, Y

' Application May 17, 1941,er alNo.'394,035

2 Claims. (otiv pso This invention relates to improvements in mechanism generally knownas Bowdenmechanism, which comprises an inner partand an outer casing whereby power may be transmitted over a curved path by relative longitudinal dis placement of the inner part and the casing. Q

' Although there is wide variety of use {for Bowden mechanisms, they are particularly adapted for use in record controlled statistical and accounting machines wherein, due to limitations of space, they are frequentlymore suitable for transmitting power than rigid Wires ormechanical linkages. Examples of the use to which Bowden mechanisms may be put are to be tound in a number of patents that relates to a cl'ass of machines generally known as Powers record controlled machines. Instancesin whichnthese mechanisms are used to transmit power frorna record'sensing mechanism to deflecting mecha nisms in a record sorting" machine are shown in the following patents to W. W. Lasker: 1,298,971, issued April 1, 1919; 1,315,370, issuedyseptember 9, 1919; 2,044,120, issued; June 16, :1936; and 2,084,850, issued June 22, 1937'. Instances in which they are used to transmit power from a record sensing mechanism to adding mechanisms or control devices in tabulating machines are shown in the following patents: ,W. W..' Lasker, 1,307,683, issuedJune 24, 1919; Lasker, 1,831',358,issue d November 10, 1931; J. M. Rand, Jr.,"et al., 2,059,277, issued- November 3, 1936;.andJfTIFerry, 2,185,841, issued January 2, 1940. Instances in which they are used to transmit power from "a keyboard to punchsetting mechanisms in a, record perforating machine are shown in the following patents: W. W. Lasker, 1,305,557, issued June 3, 1919; M. Lebeis, 1,680,054, issued August'7, 1928; W. W. Lasker, 2,124,178, issued July 19,1938; W. F. Kelley, 2,160,152, issued May 30,1939; E. Roggenstein, 2,160,171, issued Mayf30, 1939; and W, F. Kelley, 2,203,355, issued June 4,1940. These mechanisms may also be used to transmit power from a single source to a plurality of receiving points simultaneously as in patents to W. W. Lasker, 2,107,184,; issued February 1, 1938, and H. T. Anderson, 2,160,113, issued May' 30, 1939. When used as in the latter instances, these wires are commonly termed Y-wired Bowden mechanisms.

During the period that Bowden, mechanism has been used in the above types of mac h ines, its constructionand method of manufacture has been, constantly modified in an attempt to obtain a. standard device that isfsuitable "for use under each gfj the various conditions in which it'may be employed. Prior to tl'ietime of the present improvement, Bowden mechanism in gerrem -teem machines of the above types usually comprised an outer member consisting of a flexible j tubing or cylindrical casing formed of a closely coiled single wire,'similar to a helical extension spring' Furthermore, this casing Was Wound with a certain degree of initial tension to provide areasonable amount of stiffness in l the finished product. The inner member or core consisted of a single straight wire having a, diameter equal approximately to half the internal diameter oft'he casing. By this arrangement, the-core was closeenough to the casing to be supported thereby when force was applied to the" core. At the same time sufficient clearance was provided to permit unimpeded return movement of the core under the impetus of a light spring. In practice the most satisfactory results were obtained from a Bowden mechanism comprising an outer casing formed of music wire having a diameter of .030" closely wound into a coil having apitch diameter of approximately .065", and a core member formed of musid wire having a diameter-of .015".

The Bowden wire casings generally employed have been closely coiled springs. With the longitudinal resilience inherent in such a spring casing, it is evident that, when the casing is bent to transmit power in a; direction other than a straight line, the coils of the casing on the inside of the bend come together. The bending force causes a V-shaped spread between each coil starting at the inside of the bend and spreading radially outward. The greatest amount of opening movement takes place on the outside of the bend and half the spread is evident along the median of the coil. The accumulation of space caused by the spread extends the ends of the coil and causes it toswallow the core. As the coreat its opposite ends usually abuts operating'members, any shortening or take-up. of said core will render all or part of the movement of the operating members ineffective.

Under certain conditions, for exampla'when the opposite ends of the casing are fixed relative to each other and there is no excessive force applied to the core, the lengthening of the casing due to the bending action is'of no consequence. In these instances, when the casing is originally set in placein a machine the core may be inserted therein and cut to the proper length to "operate under normal working conditions. Examples of such a condition are shown in the above mentioned Patents 1,307,683, 1,680,- 054, 2,084,850, and 2,160,171.

However, in the event that the ends of the casing are movable relative to each other, or that excessive loads are applied to the core suifi cient to cause deflection of thecasing, it is apparent that the resultant lengthening of the casing changes the original adjustment and de creases the efiective thrust of the core. For example, in a condition such as that imposed in r the above mentioned Patent 2,124,178 (see Fig. 1 thereof), wherein one end of the casing is fixed to a solenoid and the other to a movable carriage in a record perforating machine, it is apparent that as the carriage moves from left toright across the machine the total of the angles subtended bythe arcs formed in the casing increases from approximately 90 to approximate- However, over aperiod of time the accumula-:

tion of dust within the casing increases the friction between the core and casing to such an extent that ultimately I a substantial portion ofthe force impressed on the core is exerted against the casing. This condition causes an increase in the bend in the casing and thereby further reduces the effective movement of the core, As a result, unless the parts are frequently disassembled, cleaned, and readjusted, the element or linkage to be actuated by the core is not moved the distance required and misoperationv ofthe machine occurs.

A coil having the characteristics of a. spring, that is, one which can be distended axially under either compressiveor tensional force and when released will spring back to its original form, will, upon being bent, expand axially because the inherent springiness will not sufficiently resist the bending stress to prevent contacting accumulation of the coils on the inside of the bend. In effect,- when the coils contact, they constitute a fulcrum for the-bending force, which is visible in the V-shaped spread of the coils in radial direction. A casing having spring action in the direction of its longitudinal axis is not; sufficiently rigid to restrict movement of the core under the conditions that obtain in perforating machines of the type disclosed in said Patent 2,124,178. In these machines the Bowden mechanism cores are actuated by key operated solenoids, and the arrangement. is such that the force applied is relativelygreat but of exceedingly short duration. As a result a substantial part of the force applied to the core is dissipated in friction against the bends in the casing andserves only to deflect the coils of the casing. Thus, as in the previously described arrangement, the actual length of the casing is increased and the effective thrust of the core is decreasedaccordingly so that misoperation of the' machine frequently occurs. Obviously, the'relative change in length of the core and casing in a Bowden mechanism so constructed becomes more pronounced as the number of bends in the casing increases.

The principal object of the-present invention is to'improve Bowden mechanisms so'as to decrease the extent of relative change inv length of the core and casing when the mechanism is bent, and to decrease the extent of deflection in the limits the casing when relatively heavy forces are applied to the core.

To this end the invention comprises a Bowden mechanism having an outer casing formed of a single Wire wound in a helical coil wherein the spring function of the coil in axial direction is substantially eliminated, the index of the coil is substantially less than that in the usual forms of compression or extension springs, and the pitch per coil is substantially greater than that in the usual forms of compression and extension springs. An embodiment of the invention is shown in the drawing, in which Fig. 3 discloses a common. type of Bowden mechanism bent into an arc;-

, Fig. 4 isthe same mechanism of Fig. 3 straight-. enedout; v

Fig. 5 represents the invention formed in an arc, and 1 Fig.6 shows the mechanism straight line.

c In the design and manufacture of helical springs for their usual uses, the customary practice is tormaintain the spring index, i. e., the ratio between the pitch diameter D (see Fig.2) of the coil and the diameter d of the wire used to form the coil, between 7 and 12 or well within defined by modern spring winding practice.

However, in the uses to which Bowden mechanisms are applied in machines of the types disclosed in the above mentioned patents it will be noted that the spring casings are not compressed or extended in the sense in which these terms are ordinarilyapplied to helical springs. In these machines it is required that a casing be sufficient-' lyfiexiblein lateral direction to' guide the axial movement of the core member around bends and,

at the same time, be sufiiciently rigid axially to I prevent appreciable change in its own. axial length. i

Bowden wire mechanisms, heretofore have us-1 ually been made with an outer spring casing, that is, alhelically wound, closely coiled wire having an inherent axially elastic characteristic. This characteristic, provided by the spring nature of the metal wire and the coiling of the same into spirallspring' form in accordance with well defined spring winding practice and design, permitsthe coil casing to be elongated under ten- I sion and returned to normal without distortion.

I have foundv that a coil having enough axial flexibility to'be recognized as possessing longitudinal} spring action is unsuitable for use as a casing for a Bowden wire core for reasons illustrated in Figs. 3 and ,4. The axially flexible Bowden mechanism casing coil ID with the coils closely woundlis the same length when straight When the coil It is bent connected parts, the coil sections forming the inner bend as defined by arc CD press against each other. The axial flexibility of 'the'casi'n'g permits'this with the result that the bending force opens the spring casing I 0 on its outer periphery. one half 'of this amount of opening or separation of the coils takes place along' the axis of the coil'with the result that the ends of of Fig. 5 in a 'core H.

In making my improved casing, I first make a helical spring in accordance with usual spring practice, and then stretch the spring longitudinally by pulling until it loses its spring'characteristic or until it will no longer spring back to its original form. In effect, it is .nolonger a spring, but a helical coil of wire that has sufficient axial rigidity to maintain the coils or convolutions in fixed permanently set spaced relation relatively to each other under normal operating conditions.

amount, of longitudinal elasticity that would characterize the coil as a spring, and as illustrated in Fig. 2, the coils are separated a pitch distance determined by the amount of longitudinal stretch necessary to produce the finished product. While this casing is rigid in longitudinal or axial direction, it is flexible laterally so that it can bend. in any direction in accordance with the requirements of operating conditions in the machine.

In Fig. 6 this axially rigid casing 2| is shown straight, and the core 20 is the same length EF as the casing. When the casing is bent as in Fig. 5, the length EF is substantially the same as the arc GH. Any difference is occasioned by the difference of the radial distance of the core 2%) beyond the mean radius of the bent casing 2|.

On the median line of the bent'casing 2|, the 'coil does not increase in length when it isbent because bending force applied to a casing, in which the convolutions are held inrigid spaced relation, causes the convolutions at the inner or compres- Such a casing is devoid of an The permanentseparation of the convolutions.

of the casing provides a Bowden mechanism that is advantageous over those wherein the casing is made from closely coiled wire. Previously, it was necessary to disassemble the mechanism, extract 'the' core from the casing, then clean and lubricate each part separately. When the parts were reassembled, readjustment was required. In my novel casing, the space between the convolutions of the coil permits ready cleaning and lubrication of the casing and core without detachment of any of the parts from the machine or from each other, and the need for adjustment after conditioning is thus eliminated.

Although this description is limited to a discussion of the uses of an improved type of Bowden mechanism as employed in certain record con trolled machines, it is apparent that Bowden mechanism constructed in accordance with my invention may be made of any suitable type of wire for use in various types of machines. While wire has been referred to, it is to be understood that any material of a suitable nature may be employed and *may be *coiledin any manner to obtain the result disclosed. For instance, it has been found that when a casing made like a spring is lengthened axially, the wire gets harder and the diameter of the coil decreases. By winding a coil of diameter larger than desired which has an inherent spring character, it can be drawn lengthwise to decrease the diameter to needed size and at the same time increase the pitch and eliminate said spring characteristic. Also, a wire of I suitable ductility may be initially wound so that sion side of the casing to approach each other an amount about equal to the amount that the outer side of the convolutions spread apart. The bending force appears to twist each convolution about its lateral axis so that the inner side and the convolutions thereof will be fixedly spaced and the coil. will have axialrigidity without any lengthening operation being necessary.

What I claim as new and desire to secure by Letters Patent is:

outer side movements of the coil convolutions in closing and opening respectively compensate for the bend and no appreciable amount of movement between theconvolutions at the median line of the casing, or overall longitudinal expansion of the casing, is evident along its axis. Hence, the:

axis of the core 20 will equal the length of the axis of the casing 2| whether the latter is bent or straight. Any bending force, whether applied by the core to the casing or directly to the casing,

willnot result in any shortening of the core relatively to the casing to render the core inefi'ective as is evident where the casing is a spring.

1. A Bowden mechanism casing comprising a laterally flexible, helically wound single wire coil having its convolutions permanently set in spaced relation to maintain axial rigidity of the convolutions under normal operating conditions.

2. In a Bowden mechanism, a casing comprising a laterally flexible, helically wound single wire coil having its convolutions permanently set in spaced relation to maintain axial rigidity of the convolutions under normal-operating conditions and a core passing through said coil.

ARTHUR NELSON. 

